The Health Effects Institute
Research Report Number 42
Does Inhalation of Methanol Vapor Affect Human Neurobehavior?
Mary R. Cook, Fred J. Bergman, Harvey D. Cohen, Mary M. Gerkovich, Charles Graham, Roger K. Harris, and Linda G. Siemann
Life Sciences Department, Midwest Research Institute, Kansas City, MO
Methanol (wood alcohol) may become an important alternative fuel for motor vehicles in the near future. The 1990 Amendments to the Clean Air Act require that, in areas of the country that have not met specific ambient air quality standards, certain increases must occur in the number of "clean-fuel vehicles." The legislation does not define "clean-fuel vehicle" in terms of fuel composition but in terms of specific performance requirements. However, methanol is specifically listed as a possible "clean alternative fuel." Methanol use in motor vehicles would probably reduce levels of several regulated air pollutants, such as ozone, particulate matter, and carbon monoxide. However, it would probably increase levels of two other pollutants: methanol and formaldehyde. Policymakers need better information on how exposure to low concentrations of these substances might affect human health and function.
Methanol is clearly poisonous at relatively high levels of exposure, but little is known about whether inhalation of low levels of methanol affects the human nervous system. If introduced as an alternative fuel, the most common human exposure to methanol would be from inhaling vapors released into the air from vehicle emissions, during refueling, and from spills. The Health Effects Institute (HEI) sponsored an exploratory study, summarized here, to see whether exposure to methanol vapor might affect the human nervous system, and if so, what would be the best experimental conditions for examining this effect.
In this pilot study, Dr. Mary Cook and colleagues exposed 12 young male volunteers to either filtered air or methanol vapor (192 parts per million) for 75 minutes. (This concentration of methanol is estimated to approach the highest concentration that individuals might experience from normal use of methanol-fueled vehicles under a worst-case scenario.) The volunteers underwent 20 commonly used tests of sensory, behavioral, and reasoning performance before, during, and after each exposure. To reduce the possible influence of suggestion, neither the chamber operator nor the subjects knew which exposures were to methanol and which were to filtered air.
RESULTS AND IMPLICATIONS
Methanol had no detectable effect on the subjects' performance for most tests. However, performance was slightly impaired in one test measuring memory and concentration. In another test, the subjects' brain wave patterns changed slightly in response to light flashes and sounds. The effects observed in this study were minor and within the range of test values for subjects exposed to air. The possibility that these results were due to chance or normal variability is supported by the lack of positive findings in related tests in which similar effects would have been expected. Nevertheless, further research, with a larger number of subjects, is needed to confirm or refute these results and to investigate other important related questions, including: Would exposure to the same or higher concentration of methanol for longer periods of time affect other populations, such as elderly men and women, and people with compromised vision? Answers to this and other questions will contribute to a sound basis on which regulatory and policy decision-makers can compare the public health benefits of methanol versus gasoline.
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